Amine/phosphate composition useful as corrosion and scale inhibitor

ABSTRACT

A COMPOSITION USEFUL AS A CORROSION AND SCALE INHIBITOR IS OBTAINED BY REACTING AN N-SECONDARY ALKYL ALKYLENE DIAMINE (E.G. CONTAINS AN AVERAGE OF 8-20 CARBON ATOMS IN THE ALKYL GROUP AND 2-4 CARBON ATOMS IN THE ALKYLENE GROUP) AND A PHOSPHATE ESTER, OBTAINED FROM EXAMPLE BY REACTING ABOUT EQUAL MOLAR AMOUNTS OF POLYPHOSPHORIC ACID AND A CONDENSATION PRODUCT OF AN ALIHATIC PRIMARY ALCOHOL (PREFERABLY CONTAINS 3-6 CARBON ATOMS) AND AT LEAST ONE MOLE (PREFERABLY 1-10 MOLES) OF AN ALKYLENE OXIDE (PREFERABLY ETHYLENE OXIDE). FINAL REACTION PRODUCT CAN HAVE A PH OF 5-9.

United States Patent Int. Cl. C02b /06 US. Cl. 210-58 2 Claims ABSTRACTOF THE DISCLOSURE A composition useful as a corrosion and scaleinhibitor is obtained by reacting an N-secondary alkyl alkylene diamine(e.g. contains an average of 820 carbon atoms in the alkyl group and 2-4carbon atoms in the alkylene group) and a phosphate ester, obtained forexample by reacting about equal molar amounts of polyphosphoric acid anda condensation product of an aliphatic primary alcohol (preferablycontains 36 carbon atoms) and at least one mole (preferably 1-10 moles)of an alkylene oxide (preferably ethylene oxide). Final reaction productcan have a pH of 5-9.

CROSS REFERENCE TO RELATED APPLICATION This is a divisional of mycopending patent application, Ser. No. 812,847, filed Apr. 2, 1969, nowabandoned and a divisional of my copending application Ser. No. 190,266,filed Oct. 18, 1971, now Pat. No. 3,787,319.

BACKGROUND OF THE INVENTION Corrosion control in the petroleum industryis obtained in general by changing the environment and/or by forming aprotective barrier on the corroding object. Corrosion inhibitors aregenerally of the neutralizing type or the film-forming type.Neutralizing inhibitors function by neutralizing the active corrodantsin the system whereas film-formers are believed to function by placing aprotective barrier between the metal and the corrosive environment.

Film-forming inhibitors used in greatest quantity in the oil industryinclude the fatty and heterocyclic nitrogencontaining compounds, such asthe amine-acid complexes and the imidazoline derivatives. In particular,fatty amines and particularly the diamines combined with fatty acidssuch as resin acids and tall oil acids, oxidized petroleum fractions andnaphthenic acids produce good film-forming corrosion inhibitors.

Applicant has discovered a composition useful, inter alia, as afilm-forming corrosion inhibitor, scale inhibitor, etc. The compositionis obtained by reacting an N-secondary-alkyl alkylene diamine and aphosphate ester.

DESCRIPTION OF THE INVENTION Examples of useful phosphate esters includethose found in US. Pat. No. 3,331,896 to Eiseman, Jr. et al. Preferredphosphate esters are obtained by reacting about equal molar amounts ofpolyphosphoric acid and the condensation product of an aliphatic primaryalcohol (contains 1 to about 12 carbon atoms and preferably containsabout 3 to about 6 or more carbon atoms) and at least about one mole,preferably about 1 to about 10 moles, of an alkylene oxide, preferablycontaining about 2 to about 4 carbon atoms, such as ethylene oxide. Thepolyphosphoric acid is composed of an equilibrium mixture oforthophosphoric, pyrophosphoric, and higher linear phosphoric acids.Commercially available polyphosphoric acids range from about 110% toabout 120% H PO and contain about to about 86.5% P 0 A more detaileddescription of useful polyphosphoric acids is found in US. 3,331,896 toEiseman, Jr. et al. For purposes of this invention, one mole ofpolyphosphoric acid is defined as one mole of P 0;, as present inpolyphosphoric acid.

Examples of N-secondary-alkyl alkylene diamines are found in US. Pat.No. 3,398,196 to Fuller, Jr. et al. Particularly useful diamines areidentified by the formula:

wherein x and y are positive integers having a sum of about 6 to about30 and n is a positive integer within the range of about 2 to about 4and preferably is 3. The polyamines are preferably oleophilic andcontain substantially saturated alkyl chains. Additional examples ofuseful diamines include those found in Product Data Bulletin, BulletinNo. 68-3, under the title Beta Amines and Derivatives, Armour IndustrialChemicals, Box 1805, Chicago, Ill. A particularly usefulN-secondary-alkyl alkylene diamine is one wherein the alkyl groupcontains an average of about 10 to about 20 aliphatic carbon atoms.

The diamine and the phosphate ester are reacted in sufficient amounts togive a resulting pH of about 5 to about 9 and more preferably about 6.5to about 7.5. A solvent compatible with the phosphate ester and diaminecan be utilized during the neutralization to facilitate mixing, e.g.,isopropyl alcohol, or a similar alcohol. Reaction temperature canpreferably be within the range of about 60 F. to about 100 F. and morepreferably about 80 F. to about F.

Compositions of this invention are especially useful as corrosioninhibitors in producing oil and gas Wells. They are also useful ascorrosion inhibitors in both liquid and gas flow lines, gas-lift wells,pumping operations, and any like operation. The composition may be addedcontinuously by means of a pump, lubricator, etc. to the casingtubingannulus, flow lines, etc. If the casing annulus of a well is blocked,that is, packed off from the tubing, the inhibitor can be added to thetubing; the production is preferably stopped during this type ofaddition. Or, the inhibitor can be added as a solid stick (i.e. thecomposition can be incorporated along with binders, Wetting agents, orother compatible agents, to form a solid article) and placed in thetubing or casing Where it melts or dissolves in the well fluids to givethe desired protection to the well.

In addition, the compositions of this invention can be squeezed into theformation-thereafter the composition is flushed out of the formationwhen the Well is produced. The latter method can impart a reasonablylong protection, e.g. 6 to 12 months to the well bore. However, theinvention is not recommended Where barium sulfate scale is principallycharacteristic of fouling production.

These compositions are useful to form protective films on any metal.Yellow metals can be coated with the composition to give protectionagainst corrosion, scale, etc. Other metals including carbon steel,stainless steel, etc. can also be effectively coated with thesecompositions.

The composition is useful in amounts sufiicient to form a mono-molecularlayer on the surface of the metal to be protected. For example, thearticle can be immersed in a dilute solution containing about 1% toabout 20% or more by Weight and preferably about 5% to about 10% byweight of the composition. Concentration of about 2 p.p.m. to about 500p.p.m. or more and preferably about 5 p.p.m. to about 100 p.p.m. of thecomposition in a major portion of the corrosive or sealing medium isuseful to protect equipment, eg tubing and casing in a well.

The following examples are presented to teach specific workingembodiments of the invention. These examples are not intended to limitthe invention in any way. Rather, all equivalents obvious to thoseskilled in the art are intended to be incorporated into the scope of theinvention as defined in the specification and appended claims. Un lessotherwise specified, all percents are based on weight.

EXAMPLE I An oil well producing about 19 parts of water to about 1 partof crude oil has a corrosion rate of 5 mils per year with a pittingtendency indicated by the following Corrator reading (Corrator is atrade name of Magna Corporation, Sante Fe Springs, Calif):

CORRATOR READING 100 scale: scale:

20 millivolts 10 millivolts A: 3 A: 2 B: +12 B: +6.5

The above data were determined after the well was cleaned by bailing andthen well was pumped for five days and the Corrator probe was placed ina flow line. The 100 scale reading indicates a pitting tendency of thusa severe pitting condition is present. The well was treated with 5gallons of an aqueous solution containing 25% tap water, 25%isopropanol, and 50% of a chemical composition obtained by neutralizinga monophosphate ester (obtained by reacting equal molar amounts ofpolyphosphoric acid and the condensation product obtained by reacting 1mole of N-butyl alcohol and 1 mole of ethylene oxide) with Duomeen L-ll(a trade name of Armour Industrial Chemicals, Chicago, Ill., identifyingan N-secondary-alkyl trimethylene diamine wherein the alkyl groupcontains an average of about 11 to about 14 carbon atoms) to a pH ofabout 7.0 at 90 F. The resulting mixture contains about equal weightamounts of the isopropyl alcohol, the monophosphate ester, and theDuomeen L-ll and the residue is water. The aqueous solution iscirculated for two hours through the annulus of the well and through thetubing. A reading on a Corrator placed in a circulating line indicatedthat the corrosion rate was now 0.7 mils per year; the pitting tendencywas drastically reduced, as evidenced by the following data:

CORRATOR READING 100 scale: 10 scale:

millivolts 10 millivolts A: +1.0 A: +1.0 B: +2.0 B: +1.2

To test the scale inhibition characteristics of the compositions of thisinvention, an apparatus was used which comprises rotating a heated metalrotor in a water solution containing the scale-forming mineral. Thistest procedure is described in an article by F. W. Jones, ChemicalInhibition of Mineral Scales, presented at The National Association ofCorrosion Engineers, South Central Region Annual Conference, Tulsa,Okla, October 1960. The heated metal rotor is easily weighed, coated,and cleaned. The rotor assembly is made of tubing and the disk or rotoris perforated metal (sheet metal) welded at the end of the tubing.Cylindrical electrical heaters watt) are mounted inside the rotor tube.The rotor is rotated at a velocity usually equivalent to about 10 feetper minute at the rotor edge. The aqueous liquid containing thescale-forming mineral, 250 milliliters, is contained in a 400 milliliterPyrex glass beaker and a thermometer is extended into the liquid in thebeaker to record the temperature. The compositions of this invention aretested for CaCO scale inhibition at F. in an aqueous solution containingtap water, 3 grams per liter of CaCO 5% by Weight of NaCl and the liquidsaturated with C0 The rotors are immersed in the compositions indicatedin Table l for 10 minutes at ambient temperature, are then washed withtap water to remove excess chemicals and are then placed in the aqueoussolution and rotated for 4.5 hours at a temperature of F. Thereafter,the rotors are cooled for one half hour and are dried and weighed. Thepercent inhibition against scale adhering to the rotor is determined byWeighing a control rotor (not treated with the composition) before andafter scaling, subtracting from this difierence the amount of scaleadhered to a test rotor (i.e. a rotor treated with the composition ofthis invention) and dividing this difference by the scale adhered to thecontrol rotor. Table 1 contains the composition used to coat the rotorand the percent inhibition against scale:

TABLE 1 Percent inhibition against scale Sample number Chemicalcomposition A 50% isopropanol and 50% of the composition obtained byneutralizing the monophosphate ester of Example I to pH of 6.0 withDuomeen L-l5 (same as Duomeen L-11 except the alkyl group contains anaverage of about 15-20 carbon atoms), this composition diluted to 20% inStoddard solvent.

B Same as A except water replaces the Stoddard solvent.

Same as A Same as A except Duomeen L-ll is substituted for Duomeen L-15and 1% of the dimagnesium salt of ethylene diamine tetraeetic acid isincorporated into the solution.

E Same as A except Duomeen L-ll is substituted for Duomeen L-15 andneutralized to pH of 7.0 and 1% of a nonionie wetting agent is added tothe solution (reaction product of 1 mole octyl phenol and 15 moles ofethylene oxide).

F 50% isopropauol and 50% of the composition obtained by neutralizing amonophosphate (obtained by reacting equal molar amounts ofpolyphosphoric acid and the condensation product of one mole of iso-amylalcohol and 4.0 moles of ethylene oxide) to a pH of 6.0 with DuomeenL-ll, this composition diluted to 20% with water.

G Same as F except the monophosphate contains 5.1 moles of ethyleneoxide and Duomeen L-15 is substituted for Duomeen L-ll to neutralize toa pH of 7.

What is claimed is:

1. A method of inhibiting formation of scale deposits on surfacesexposed to water containing salts of alkalineearth metals in solution,the method comprising adding to the water in amounts sufiicient toinhibit deposition of salts of the alkaline-earth metals, a phosphorouscontaining compound obtained by neutralizing to a pH of about 5 to about9 at a temperature less than about 100 F.,

(1) a phosphate ester obtained by reacting about equal molar amounts ofpolyphosphoric acid (one mole of polyphosphoric acid is' defined as onemole of P 0 as present in polyphosphoric acid) and a condensa- 5 6 tionproduct of an aliphatic primary alcohol con- References Cited taining 1to about 12 carobn atoms and about 1 UNITED STATES PATENTS to about 10moles of an alkylene oxide containing about 2 to about 4 carbon atoms,with 3,462,365 8/1969 Vogelsang 252'180 X (2) an N-secondary alkylalkylene diamine wherein 5 3,597,352 8/1971 Stanford et 3,620,97411/1971 Stanford et a1 252-180 X the alkyl group contains an average ofabout 7 to about 31 carbon atoms and the alkylene group contains about 2to about 4 carbon atoms. HERBERT GUYNN Pnmary Exammer 2. The method ofClaim 1 wherein about 2 p.p.m. to U S C1 XR about 500 p.p.m. of thephosphorous containing com- 10 252 8 55 B 180 pound is added to thewater.

